Ventilating systems are commonly used to maintain environmental standards in industrial, commercial and farming facilities, such as foundries, factories, metal finishing areas, work shops, service areas, warehouses, meeting halls, recreational buildings, animal nursery and feeder houses, and other facilities of many diverse types. Ventilation systems for such facilities are necessary to remove excess heat, discharge pollutants and to maintain a healthful, comfortable environment. Unfortunately, safety, health and economic considerations are at odds with one another in that air which has been heated or cooled at substantial expense is virtually thrown away by the conventional ventilation process. In the case of a heated facility, the exhaust air of the ventilation process contains not only the sensible energy expended in increasing the supply air temperature but the latent energy represented by the vaporized water required to adequately humidify. With great pressure on power-producing utilities and the ever-increasing cost of fuels for heating and cooling, there is a great need to recover thermal energy from the exhaust air of all high performance ventilation systems.
One approach to thermal energy recovery in ventilation systems involves the use of a heat exchanger through which exhaust air is passed in one direction and supply air is passed in the opposite direction. Prior art systems using this approach produces a periodic reversal of air flow direction; this results in a quantity of trapped exhaust air which is returned to the ventilated area during each cycle of operation. Moreover, reversed-flow systems are not compatible with standard vent location technology; i.e., high level exhaust and low level supply.
A non-reversing flow system is made possible through the use of a rotating wheel heat exchanger as well as by non-rotating cross-flow heat exchangers. Prior art heat exchangers of these types have been constructed from metals such as stainless steel, and from certain ceramics such as aluminum oxide and silicon carbide. Such materials, while structurally sound, are expensive and have little or no capability of storing and releasing moisture.